/* =============================================================

	Smooth Scroll v4.5
	Animate scrolling to anchor links, by Chris Ferdinandi.
	http://gomakethings.com

	Additional contributors:
	https://github.com/cferdinandi/smooth-scroll#contributors

	Free to use under the MIT License.
	http://gomakethings.com/mit/

 * ============================================================= */

window.smoothScroll = (function(window, document, undefined) {

	'use strict';

	// Default settings
	// Private {object} variable
	var _defaults = {
		speed : 500,
		easing : 'easeInOutCubic',
		offset : 0,
		updateURL : false,
		callbackBefore : function() {
		},
		callbackAfter : function() {
		}
	};

	// Merge default settings with user options
	// Private method
	// Returns an {object}
	var _mergeObjects = function(original, updates) {
		for ( var key in updates) {
			original[key] = updates[key];
		}
		return original;
	};

	// Calculate the easing pattern
	// Private method
	// Returns a decimal number
	var _easingPattern = function(type, time) {
		if (type == 'easeInQuad')
			return time * time; // accelerating from zero velocity
		if (type == 'easeOutQuad')
			return time * (2 - time); // decelerating to zero velocity
		if (type == 'easeInOutQuad')
			return time < 0.5 ? 2 * time * time : -1 + (4 - 2 * time) * time; // acceleration until halfway, then deceleration
		if (type == 'easeInCubic')
			return time * time * time; // accelerating from zero velocity
		if (type == 'easeOutCubic')
			return (--time) * time * time + 1; // decelerating to zero velocity
		if (type == 'easeInOutCubic')
			return time < 0.5 ? 4 * time * time * time : (time - 1) * (2 * time - 2) * (2 * time - 2) + 1; // acceleration
																																																			// until halfway,
																																																			// then
																																																			// deceleration
		if (type == 'easeInQuart')
			return time * time * time * time; // accelerating from zero velocity
		if (type == 'easeOutQuart')
			return 1 - (--time) * time * time * time; // decelerating to zero velocity
		if (type == 'easeInOutQuart')
			return time < 0.5 ? 8 * time * time * time * time : 1 - 8 * (--time) * time * time * time; // acceleration until
																																																	// halfway, then
																																																	// deceleration
		if (type == 'easeInQuint')
			return time * time * time * time * time; // accelerating from zero velocity
		if (type == 'easeOutQuint')
			return 1 + (--time) * time * time * time * time; // decelerating to zero velocity
		if (type == 'easeInOutQuint')
			return time < 0.5 ? 16 * time * time * time * time * time : 1 + 16 * (--time) * time * time * time * time; // acceleration
																																																									// until
																																																									// halfway,
																																																									// then
																																																									// deceleration
		return time; // no easing, no acceleration
	};

	// Calculate how far to scroll
	// Private method
	// Returns an integer
	var _getEndLocation = function(anchor, headerHeight, offset) {
		var location = 0;
		if (anchor.offsetParent) {
			do {
				location += anchor.offsetTop;
				anchor = anchor.offsetParent;
			} while (anchor);
		}
		location = location - headerHeight - offset;
		if (location >= 0) {
			return location;
		} else {
			return 0;
		}
	};

	// Determine the document's height
	// Private method
	// Returns an integer
	var _getDocumentHeight = function() {
		return Math.max(document.body.scrollHeight, document.documentElement.scrollHeight, document.body.offsetHeight,
				document.documentElement.offsetHeight, document.body.clientHeight, document.documentElement.clientHeight);
	};

	// Convert data-options attribute into an object of key/value pairs
	// Private method
	// Returns an {object}
	var _getDataOptions = function(options) {

		if (options === null || options === undefined) {
			return {};
		} else {
			var settings = {}; // Create settings object
			options = options.split(';'); // Split into array of options

			// Create a key/value pair for each setting
			options.forEach(function(option) {
				option = option.trim();
				if (option !== '') {
					option = option.split(':');
					settings[option[0]] = option[1].trim();
				}
			});

			return settings;
		}

	};

	// Update the URL
	// Private method
	// Runs functions
	var _updateURL = function(anchor, url) {
		if ((url === true || url === 'true') && history.pushState) {
			history.pushState({
				pos : anchor.id
			}, '', anchor);
		}
	};

	// Start/stop the scrolling animation
	// Public method
	// Runs functions
	var animateScroll = function(toggle, anchor, options, event) {

		// Options and overrides
		options = _mergeObjects(_defaults, options || {}); // Merge user options with defaults
		var overrides = _getDataOptions(toggle ? toggle.getAttribute('data-options') : null);
		var speed = parseInt(overrides.speed || options.speed, 10);
		var easing = overrides.easing || options.easing;
		var offset = parseInt(overrides.offset || options.offset, 10);
		var updateURL = overrides.updateURL || options.updateURL;

		// Selectors and variables
		var fixedHeader = document.querySelector('[data-scroll-header]'); // Get the fixed header
		var headerHeight = fixedHeader === null ? 0 : (fixedHeader.offsetHeight + fixedHeader.offsetTop); // Get the height
																																																			// of a fixed
																																																			// header if one
																																																			// exists
		var startLocation = window.pageYOffset; // Current location on the page
		var endLocation = _getEndLocation(document.querySelector(anchor), headerHeight, offset); // Scroll to location
		var animationInterval; // interval timer
		var distance = endLocation - startLocation; // distance to travel
		var documentHeight = _getDocumentHeight();
		var timeLapsed = 0;
		var percentage, position;

		// Prevent default click event
		if (toggle && toggle.tagName === 'A' && event) {
			event.preventDefault();
		}

		// Update URL
		_updateURL(anchor, updateURL);

		// Stop the scroll animation when it reaches its target (or the bottom/top of page)
		// Private method
		// Runs functions
		var _stopAnimateScroll = function(position, endLocation, animationInterval) {
			var currentLocation = window.pageYOffset;
			if (position == endLocation || currentLocation == endLocation
					|| ((window.innerHeight + currentLocation) >= documentHeight)) {
				clearInterval(animationInterval);
				options.callbackAfter(toggle, anchor); // Run callbacks after animation complete
			}
		};

		// Loop scrolling animation
		// Private method
		// Runs functions
		var _loopAnimateScroll = function() {
			timeLapsed += 16;
			percentage = (timeLapsed / speed);
			percentage = (percentage > 1) ? 1 : percentage;
			position = startLocation + (distance * _easingPattern(easing, percentage));
			window.scrollTo(0, Math.floor(position));
			_stopAnimateScroll(position, endLocation, animationInterval);
		};

		// Set interval timer
		// Private method
		// Runs functions
		var _startAnimateScroll = function() {
			options.callbackBefore(toggle, anchor); // Run callbacks before animating scroll
			animationInterval = setInterval(_loopAnimateScroll, 16);
		};

		// Reset position to fix weird iOS bug
		// https://github.com/cferdinandi/smooth-scroll/issues/45
		if (window.pageYOffset === 0) {
			window.scrollTo(0, 0);
		}

		// Start scrolling animation
		_startAnimateScroll();

	};

	// Initialize Smooth Scroll
	// Public method
	// Runs functions
	var init = function(options) {

		// Feature test before initializing
		if ('querySelector' in document && 'addEventListener' in window && Array.prototype.forEach) {

			// Selectors and variables
			options = _mergeObjects(_defaults, options || {}); // Merge user options with defaults
			var toggles = document.querySelectorAll('[data-scroll]'); // Get smooth scroll toggles

			// When a toggle is clicked, run the click handler
			Array.prototype.forEach.call(toggles,
					function(toggle, index) {
						toggle.addEventListener('click', animateScroll.bind(null, toggle, toggle.getAttribute('href'), options),
								false);
					});

		}

	};

	// Return public methods
	return {
		init : init,
		animateScroll : animateScroll
	};

})(window, document);
